Post a couple of pictures.....may help diagnose the problem for you Craig  

Thanks Craig, that is a good idea. The first picture shows what appears to be the lower copper spring/prong is bent upwards.

Couldn't it be the top piece to be cracked and soon to break? That's my fear each time I need to remove the cartridge. Those plastics are very old and prone to break and I also know there is 3D print model available around and people who sell that part. Worth a look.  

It appears the cartridge body grounding contact is not being inserted properly. There is a small cutout at the bottom rear of the cartridge that receives this copper contact.

Be very careful when removing or installing the cartridge, the plastic connector will be very brittle and susceptible to fracture, many have suffered this fate. As Mark says it looks very much like the cartridge isnt seated correctly on the grounding tab (copper spring that grounds and also helps keep the cartridge in place) make sure the slot at the bottom of the cartridge is free of any debris. These arms can be repaired however its a fraught excercise that requires a degree of destruction prior to rebuild, and of course purchase of custom 3d printed parts, available from Rudi at a cost....dont bend the copper spring, is meant to be shaped to fit....there is a distict "click" when the cartridge is fitted correctly.

Thank-you for the detailed response.  Nothing feels loose, I have tried 3 cartridges in this arm that insert and work in another 4002 without any problem.  I will try to get a better look at what is going on.  Are the 3D printer parts available through this site?  I did a search for Rudi and two users popped up.  Thank-you.

The insert that Craig has a picture of is different than yours which may be the problem. Not that your leading edge is not beveled like stock ones. This may have been a 3D print attempt at a replacement and is likely causing it to not seat properly.  The arm can be carefully removed be removing the two top screws under the cover and desoldering the very fine enameled copper wires (marking them first. The cartridge holder is usually tacked-glued and I have removed them using a chop stick or equivalent to tap it out from the rear. However, as this looks like a repair attempt with a non-B&O part it is unclear how it was affixed so I would proceed cautiously. It is safe to apply a heat gun (low) to help loosen the glue.

Check out these two links....there are a couple of different designs.... http://beolover.blogspot.com/2016/02/beogram-4000-replacing-broken-mmc-mount-with-3D-printed-replacement.html https://beolover.blogspot.com/2020/08/beogram-4000-mmc-cartridge-mount-replacement.html